Prior sleeves that have been deployed in cementing service have been based on the concept of providing opposed piston areas exposed to tubing pressure that are of different dimensions so that raising the tubing pressure will create a sufficient net force to in theory overcome seal friction and move the sleeve to the open position. One such design is the Halliburton Initiator Sliding Sleeve that has a larger upper seal diameter than a lower seal. Raising tubing pressure creates a net differential force and the piston is allowed to move because there is an atmospheric chamber between the upper and lower seals. The problem is that to get the lower seal to be smaller than the upper seal to create the desired net force in the needed direction, the wall of the sleeve adjacent the lower seal and the atmospheric chamber has to be reduced so that the sleeve can shift while the volume of the atmospheric chamber is reduced.
The wall of the sleeve in the area of the atmospheric chamber sees substantial differential pressure and can flex or bend. When that happens the sleeve gets stuck and the desired port opening in the housing fails to occur.
Apart from these designs there are sleeves that respond to tubing pressure with an associated piston that is open on one side to tubing pressure and on the other side to annulus pressure. Such a design is illustrated in US Publication 2011/0100643. This design cannot be used in cementing applications as the filling up of the annulus with cement can block access to annulus pressure. Furthermore, there is a leak path potential from the tubing to the annulus through a piston seal leak.
Various pressure operated sleeves for downhole use are shown in U.S. Pat. Nos. and Publications: U.S. Pat. Nos. 7,703,510; 3,662,834; 4,330,039; 6,659,186; 6,550,541; 5,355,959; 4,718,494; 7,640,988; 6,386,289; US 2010/0236781 A1; U.S. Pat. Nos. 5,649,597; 5,044,444; 5,810,087; 5,950,733; 5,954,135; 6,286,594; 4,434,854; 3,189,044; 6,948,561; US Publication 20120006553; U.S. Pat. No. 8,171,994; US Publication 2011/0114324; US Publication 2012/0186803; U.S. Pat. Nos. 4,991,654; 5,325,917; US Publication 2012/0048559; US Publication 2011/0278017; U.S. Pat. Nos. 6,308,783 and 6,722,439.
More noteworthy with respect to the present invention is Jasser U.S. Pat. No. 7,841,412 that couples a sleeve with a flapper at the top that closes with pressure delivered from above the closed flapper to then cycle the sleeve using a j-slot so that ultimately a lateral port is opened or closed. The application is to prevent fluid loss during treatment and the design is impractical in a cementing application.
What is needed and provided by the present invention is an actuation technique for a sliding sleeve to open a port that responds to tubing pressure but addresses the flexing or bending problem associated with prior designs so that reliable movement of the sleeve is obtained. In the preferred embodiment the sleeve has differential piston areas so that applied pressure displaces the sleeve against spring bias which preferably is a series of Belleville washer stacks associated with modular mandrel components to obtain the desired opposing force to the movement initiated with pressure applied to differential piston areas. An indexing feature is located between the sleeve and the mandrel passage wall and on a predetermined number of cycles disables the Belleville washer stacks from biasing the sleeve in an opposed direction as when pressure is applied. At this time the pressure in the mandrel acting on the differential piston area simply shifts the sleeve to open a lateral port so that fracturing through the cement that was earlier placed with the port closed can take place.
Those skilled in the art will better appreciate more aspects of the invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.